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ATSE > Chapter 3 - Software architectures and their trade-offs > Flashcards

Chapter 3 - Software architectures and their trade-offs Flashcards

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1
Q

What is a Distributed System?

A

Collection of independent Computers that appear to be a single coherent system

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2
Q

What does Reliability mean in the context of distributed System

A

Probability of a system to perform its required functions under stated conditions for a specified period of time.

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3
Q

What does Availability mean in the context of distributed System?

A

Proportion of the time a system is in a functioning state, i.e., can be used.
Five nines is 0.99999 or 99.999% available

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4
Q

How is Availability usually measured (nines)

A

Class of 9s ->
1 nine: up to 35.5 day / year
4 nines: up to 52.56 min / year
9 nines: up to 31.536s / year
downtime etc

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5
Q

Availability vs reliability

A

Server may never be down but return false result’s

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6
Q

What does Transparency mean in the context of distributed System?

A

Making the complexity of the system invisible or transparent. We want to create illusion of simplicity
e.g hide the data location info,
hide the fact that server went down and session was moved to a different one. etc

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7
Q

What is Middleware?

A

Services and Abstractions that help accomodate the distributed application. e.g Messaging we implentented in CBDP or webservices

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8
Q

How does a Typical Mainframe Model looks like?

A

Network in the middle
Terminals am Rande
Hauptserver (Mainframe) macht alles

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9
Q

What are Pros of a Typical Mainframe Model

A

Single point of administration
Simple architecture and low bandwidth
Little hardware maintanance

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10
Q

What are Cons of a Typical Mainframe Model

A

Single point of failure
Bottlenecks due to sharing of the data
Mainly console programms

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11
Q

How does a Three layered client / server arch looks like?

A

Client uses browser to render data
(Web / app) Server has:
1. Presentation Layer
2. Business Layer
3. Data Layer

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12
Q

What is a part of Presentation Layer of three layered client / server arch

A

UI Components and UI all together

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13
Q

What does Business Layer of the three-layered client server arch consists of

A

Application facade,
Business Components, entities(DTO) and workflow

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14
Q

What does Data Layer of three layered client server arch consists of

A

Data access (JPA)
Data utilities(BE)
Service agents(repo in bierkasse)

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15
Q

What are the pros of a Three layered client server arch

A

No single point of failure
Scalability of the architecture
Flexibility of the architecture

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16
Q

What are Subprograms in DB

A

PL / SQL Blocks (procedure / function) that take params. difference between procedure and function - one returns value the other is void

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17
Q

What are pros of Stored Procedures

A

Better reusability,
Contentarisation - stuff meant to be done on DB is done there
with it security, maintainability etc.
Less communication - no need for sending detailed instructions

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18
Q

What are cons of Stored Procedures

A

Potentially easier to change (no need for deployment)
Portability issues
Testing - requires a special setup

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19
Q

What is data warehousing (DW)

A

Collection of tools, methods and others that allow managers and analysts conduct data analysis in decision-making processes

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20
Q

Biggest problems of Data Analysis

A

Heterogeneous sources with similar / same data
bad Data quality
Data is volatile

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21
Q

What is data mart?

A

It’s a subset or aggregation of data stored in the primary warehouse (like a part athena)

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22
Q

Difference between OLTP (online transaction processing) and OLAP (online analitical processing)

A

OLTP DB are semi big, have many users are structured, repetitive good for aplication oriented day to day operations.

OLAP are very big, have less users are ad hoc and process complex queries with mostly read only help with particular subject on decision making.

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23
Q

What is a Data qube?

A

is a tool in OLAP, based on group by queries, allows for good visualization by slicing the data

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24
Q

What is meant by ETL (Extract, transform, load) and what problems come with it?

A

Data originates in different clusters / tables and has different formats
It needs to be extracted and trasformed into a single type that can be loaded into DW
It is by far the most complex part of DW development as almost 80% of dev time is spent here.

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25
Central DW Arch
Simple, all data is in one central DW
26
Federated DW Arch
Data is stored in Data marts which contain the parts of data relevant to different e.g departments main DW is logical a.k.a virtual It allows for better performance due to distribution but is more complex to maintain
27
Tiered DW Arch
Central DW is materialized, data is then distributed to data marts that can be further divided into more data marts creating a type of a redundant tree. Offers great performance on reads as it is redundant and well distributed, however it is hard to manage and complex to implement.
28
Big issues in DW
Metadata is needed as in OLAP the information how the data was created is relevant Creation of a DW takes long time and resources, Often fails at lack of knowledge, costs, ethical issues etc.
29
What is Big data?
It relates to datasets that are that big, that managing them in a usual way becomes awkward and problematic.
30
Key computing resources in Big Data
Memory, Storage, Network
31
Big data - Challenges
Most important - Scalability!!!! What data is important to collect? (in times of AI) - definitely not what we already know Creating system with little overhead
32
Big Data - Vertical Scaling
lower / higher capacity e.g 2GB -> 4GB RAM
33
Big data - Horizontal scaling
more /less units (usually on demand) 1 EC2-> 2 EC2
34
Compare Horizontal & Vertical Scaling
Horizontal is usually less expensive instantly available, can be automated and not limited by hardware capacity. Vertical scaling is more expesive (specialized servers), usually requires additional setup and might be limited by hardware capacity (there is only as much RAM a PC can handle)
35
Horizontal Partitioning (Sharding)
!= data pool Used to partition data without it's replication. used in NoSQL based DB like mongoDB etc. Each shard represents single node in a cluster. Requires a central lookup e.g hash table to know where an element is located
36
Sharding - Name strategies
Lookup, Range, Hash
37
Sharding - Lookup Strategy
Map of all shards
38
Sharding - Range Strategy
Every Shard responsible for different ranges ordered by a shard key.
39
Sharding - Hash Strategy
Hashfunction points to a shard idea is to counteract potential hotspots as in range
40
NoSQL Databases idea
Schema free (non-relational), horizontally scalable
41
Key-Value-Store Redis
Example of a fast key-value-store Used e.g in real-time analytics, stock-prices and many more used by Twitter, Github, StackOverflow
42
Key-value-store Bigtable (Google)
Bigtable map looks like follows: row key, column key, timestamp Good for additions, but not good for modifications
43
how does Document-oriented DB store information
Json like storage e.g. Mongo db
44
What is better in document-oriented DB
Documents are independent meaning their structure can be changed as we go Application logic is easy as it transforms the entities from code directly to documents in the database and vice versa (no mapping needed) Semi structured data allows more intercompatibility in case of a migration - no need to know it's information schema
45
Graph Databases
Idea is to create free floating Objects that are interconnected by the meaning. Thanks to the materialization of relationships at the creation level there is no penalty for browsing them at a later stage, allowing constant access time. E.g Neo4j
46
What are the steps in Processing Big Data
1. Iterate over the data (large number of records) 2. Extract sth of interest from each 3. Shuffle and sort for intermediate results 4. Aggregate back for a full view 5. Generate the final output => MapReduce
47
What is a webservice?
Component wrapped behind a standardized interface e.g REST / SOAP
48
Biggest advantage of Webservices
Can be called across platforms and operating systems regardless of programming language, at the same time allowing for cross use from different applications.
49
How does SOAP / WSDL work?
Consist of Envelope that contains Header and body. Body then cointains information in form of a xml file. It is sent over HTTP / SMTP Hint: Used in critical services
50
What is SOA?
Service - oriented Architecture It's design and the scale of it that matters here. e.g Event-based interaction Language independence e
51
What are the principles of SOA?
Standardized Contract - default way of accessing all services Abstraction - hide as much as possible Reusability - service should be resources Loose Coupling - little dependencies Stateless - only then stateful when needed Discoverability
52
How does a service discovery works
When it launches it registers itself with a registry / load balancer and can be utilized from there.
53
Pros / Contras of SOA
Multi-Languge, Loosely Coupled, Independent of vendor or tech Cons: No service ecosystem, Complex, not easily scalable, less agile thourgh hardcoding and dependencies
54
What is REST?
architectural STYLE that exposes resources on a networked system not a protocol or specification
55
What is REST Resource ?
A thing that: is unique, more then just ID provides context, is reachable within addressable universe (URL / URN) e.g Website, resume, aircraft, employee, application, printer, song etc
56
REST: Statelessness
URI ( URL/URN) needs to contain a state within it, or be given it e.g: https://www.google.de/search?q=cloud&ie=utf-8&oe=utf- 8&client=firefox-b-ab&... No client application state should be stored by the server. Important Resource state != Application state
57
What are possible REST: Resource representations?
current state of a resource e.g a list of open tickets in XML/JSON.HTML/CSV etc metadata of the resource - cover image, reviews, stock-price etc
58
What does a Safe Operation on REST mean?
Read-only - nothing will change based on the operation E.g GET
59
What does a Idempotent Operation on REST mean?
Operation will have the same effect no matter number of times executed. E.g PUT, DELETE
60
What is Devops?
“DevOps is a set of practices intended to reduce the time between committing a change to a system and the change being placed into normal production, while ensuring high quality.”
61
What is a microservice architecture?
Software suites that can independently deployed with certain common characteristics such as business capability, automated deployment or the decentralized control of data.
62
How is microservice architecture build up?
Each user request is then satisfied in some order of services Most services are private and not visible on the outside All Services are independently deployable and updateble Services are organized around business capabilities instead of resources etc
63
Differences between Monoliths and Microservices?
Monoliths put all functionality into one big process. Microservices split it by different services. This allows Microservices to be easier scalable as the monolith must be replicated in whole, while microservices can have single services duplicated.
64
How do microservices communicate with each other
All Services communicate via interfaces (REST, or lightweight "dumb" pipe messaging e.g RabbitMQ / ZeroMQ)
65
Patterns in Microservices
To adress the common problems some patterns have developed. E.g service-per-container, service-discovery, db-per-service or shared db
66
Who are the actors in the Cloud
auditor, broker, carrier, consumer, provider
67
What does a cloud broker do?
Manages the use, performance and delivery of cloud services. Also negotiates relationships between cloud providers and consumers.
68
What does a cloud auditor do?
Conducts assessments of cloud services, IT systems, performance and security
69
What does a cloud carrier do?
Provides connectivity and transport to and from the cloud
70
What are essential characteristics of cloud?
on-demand self-service broad network access, resource pooling rapid elasticity measured service
71
What does On-demand self-service mean in the context of cloud?
Computing capabilities are easly provisioned as needed without human interaction with the service provider
72
What does Resource pooling mean in the context of cloud?
Providers resources are serving multiple consumers using a multi tenant model.
73
What does rapid elasticity mean in the context of cloud?
Quick scalability in/out is possible even automatically. E.g DNS / load balancing
74
What does Measured service mean in the context of cloud?
Automatic control and optimization of resources Consumer ensuring to have a process detecting idle resources
75
What is a dynamic scalability architecture?
System with predefined scaling condition which trigger allocation of IT resources from the resource pools.
76
What are types of dynamic scalability architecture?
horizontal - e.g more instances vertical - e.g more RAM relocation - e.g move to different device, that e.g has more I/O capacity

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